1. Field of the Invention
This invention relates to a novel method for preparing an N.sup.6,8-disubstituted 3',5'-cyclic adenosine monophosphate (hereinafter referred to as N.sup.6,8-disubstituted CAMP) and a salt thereof.
2. Description of the Prior Art
CAMP and its derivatives have various physiological activities and are promising as medicinal agents in a variety of application fields. The N.sup.6,8-disubstituted CAMP has excellent pharmacological activities including antiinflammative activity, inhibitory activity of platelet aggregation, hypotensive activity, cardiotonic activity and antitumor activity.
As the prior methods for preparing an N.sup.6,8-disubstituted CAMP, there have been known a method wherein a 6-chloro-8-substituted 9-.beta.-D-ribofuranosylpurine 3',5'-cyclic phosphate obtained by chlorination of the 6-position of 8-substituted inosine 3',5'-cyclic phosphate is reacted with an alkylamine [process I: U.S. Pat. No. 4,058,659; Journal of Medicinal Chemistry, 23, 242-251 (1980)],